Conventional mechanically actuated fuel injectors include a tappet assembly having a tappet and a plunger that, typically, are mechanically coupled to one another. A rocker arm assembly moves with each rotation of an engine camshaft, moving the tappet, and thus the plunger, downward. The plunger, disposed within a plunger bore of the fuel injector, pressurizes fuel during this downward stroke, and is retracted by a spring during fuel injection events. The spring, which is always compressed, also maintains the tappet in contact with the rocker arm assembly throughout the operation of the system.
Typically, these fuel injectors include a guided tappet, as shown in U.S. Pat. No. 6,607,149. Specifically, the tappet may include a sleeve portion that telescopically receives a portion of the fuel injector body. This arrangement is designed to maintain alignment of the tappet with a centerline axis of the fuel injector and, therefore, reduce side loading of the components. While performance of these fuel injectors may prove acceptable, there remains a risk of seizure or failure between the interacting components. For example, the high operating temperatures and pressures may cause component expansion, which may distort the clearance between the tappet sleeve and the external guiding surface of the fuel injector body. In addition, contaminants may break down the fluid film between the internal surface of the tappet sleeve and the external surface of the fuel injector body, thus causing wear or eventual failure of the moving components. Further considerations may include the added costs of external or, alternatively, internal guiding features.
Oftentimes, these guided tappets are prevented from accidentally disconnecting from the fuel injector body during transport using a cylindrical pin that engages a portion of the tappet assembly. Since transport may include shipping and handling of the fuel injector, it is possible for side forces occurring during these stages to cause the tappet assembly to become misaligned with a centerline axis of the fuel injector, especially since the pin engages only one side of the tappet assembly. In addition, since transport occurs without the substantial lubrication that exists after installation, it is possible for a misalignment to cause scuffing, seizure, or, at the very least, difficulties during installation.
The present disclosure is directed to one or more of the problems set forth above.